net: fix incorrect original ingress device index in PKTINFO

When we send a packet for our own local address on a non-loopback
interface (e.g. eth0), due to the change had been introduced from
commit 0b922b7a ("net: original ingress device index in PKTINFO"), the
original ingress device index would be set as the loopback interface.
However, the packet should be considered as if it is being arrived via the
sending interface (eth0), otherwise it would break the expectation of the
userspace application (e.g. the DHCPRELEASE message from dhcp_release
binary would be ignored by the dnsmasq daemon, since it come from lo which
is not the interface dnsmasq bind to)

Fixes: 0b922b7a

 ("net: original ingress device index in PKTINFO")
Acked-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: Wei Zhang <asuka.com@163.com>
Signed-off-by: David S. Miller <davem@davemloft.net>